During routine physical examination, a significant cardiac murmur (Grade V out of VI, holosystolic) was discovered in an adolescent female baboon. Subsequent work-up revealed palpable fremitus in the animal's right inguinal region, suggestive of an arterio-venous fistula (A-V shunt). Radiographs showed a grossly enlarged heart with possible associated pulmonary edema. Echocardiography confirmed that the heart was dilated, hypertrophic and hyperdynamic, due to volume overload from the A-V shunt. Ultrasound of the inguinal region confirmed the presence of a vascular communication between the femoral artery and vein (an A-V shunt). The origin of this baboon's shunt is unknown, but possible etiologies include a congenital abnormality or an iatrogenic cause subsequent to venipuncture. A surgical ligation of the shunt was performed and, since that time, the baboon's cardiac abnormalities have been monitored. While the animal's heart remains somewhat enlarged, the murmur is no longer present, heart function is adequate, the lungs appear to be clear and the inguinal fremitus is no longer palpable. The surgical correction of this A-V shunt appears to have been curative and the animal is now available for assignment to the colony breeding program.